1. Field of the Invention
The present invention relates generally to the art of electronic autostereoscopic flat panel displays and more specifically to producing high quality moving images in both in the stereoscopic and planar (non-stereoscopic) modes on an electronic autostereoscopic flat panel display.
2. Description of the Related Art
An autostereoscopic display, in particular the kind using a microlens array in order to be of general usefulness, must function in both the autostereoscopic and planar modes. The problem that faces the designer is that the microlens array, with its multiplicity of refractive elements, while producing an autostereoscopic image in association with properly encoded or mapped data, will reduce the effective resolution of the display when planar data is viewed. The usefulness in the planar mode is so compromised that performance is unacceptable.
As used herein, the terms “lens sheet,” “lenticular screen”, or “lens screen” are used synonymously, and an individual microlens element is sometimes called a lenticule, lenticle, or a lenslet.
In the current state of autostereoscopic displays, a need exists for applications such as autostereoscopic digital signage. Such a design would preferably produce a good quality planar result, allowing the owner of such digital signage equipment to play her legacy planar content. In addition, a computer desktop monitor configured appropriately can be used for typical planar applications such as word processing, and also used for autostereoscopic visualization applications. The technology can be applied to a television receiver so that current planar content can be enjoyed at one moment, and at the next, autostereoscopic images may be viewed without the user having to lift a finger.
Certain assumptions are made throughout this disclosure. First, the disclosure assumes the use of a flat panel, typically a liquid crystal or a plasma display, but other types are also to be considered without any loss of generality, such as organic light-emitting diodes. And, although this discussion assumes the use of a refractive microlens array, this disclosure also applies to a raster barrier selection device.
Certain designers have suggested features that would allow an autostereoscopic display to function equally well in both the autostereoscopic mode and the planar mode. The most obvious is to use a removable microlens array. Such an array is a flat sheet made up of a multiplicity of lenslets, and can usually be removed from its position in intimate contact with the display surface. One concern with this approach is achieving proper juxtaposition of the array with respect to the underlying display. Once returned to the display surface, each lens element must be precisely aligned with its associated sub-pixel. In addition, many users find storing the lens sheet inconvenient. Both storage and alignment are factors of concern, and the solution is somewhat inelegant.
A method for overcoming the alignment concerns raised by the removable lens sheet approach involves the use of a supplemental refractively neutralizing lens sheet which has negative-going or convex shaped lenslets which, when placed in juxtaposition with the primary lens sheet, neutralize the effects of the lens sheet. The benefit of this approach is that there are no alignment issues with regard to the primary microlens array. However, the process of placing and removing the lens sheet is hardly transparent to the user and generally inconvenient.
Yet another solution is an electro-optically switchable lens sheet. Such a lens sheet is able to turn on and off the refractive properties of the lenticules using a specially designed liquid crystal cell. The lenticules are formed on the inside of the cell. The refractive properties of the cell may be neutralized by electro-optically changing the refractive property of the liquid crystal material. Such an elegant approach involves the use of two liquid crystal displays, the variable electro-optical microlens array itself and the image forming display. Such an arrangement will substantially increase the cost of the product, but if properly implemented and realized, such a design can be transparent to the user.
The manufacturer Sharp Electronics Corporation produces autostereoscopic display products using two liquid cells. The selection device in certain Sharp products lies between the display proper and the light source and forms a switchable inverted raster barrier device. The liquid crystal shutter forms parallel ruling that is turned on or off in the autostereoscopic and planar modes respectively. In present designs, the Sharp device uses only two views and suffers from a tiny viewing zone, which is very undesirable. The Sharp design uses two liquid cells in optical series, has the disadvantage of increased cost, and suffers from reduced brightness.
These solutions, and others like them, have been proposed in the literature because designers have sought a display that functions in both in the autostereoscopic and the planar modes and exhibits excellent overall viewing characteristics and ease of use. For the reasons given above, previously available displays may not be entirely practical in terms of price and performance.
Such a display may well be used with a desktop PC, in which case the microlens array will need to pass through fine text and icons. For example, a minimum resolution requirement for a decent quality desktop monitor is on the order of 1080×1024 pixels, at a minimum. Certain users may not be happy with this and would require something more like 1280×1024 pixels, or higher. In the realm of the home television, the maximum display requirement is 1920×1080 to conform to the highest quality HDTV mode.
It would therefore be desirable to offer an autostereoscopic display capable producing both a high quality autostereoscopic image and a high quality planar image that overcomes the design issues associated with previous designs. Such a design may minimize user effort and may be realized at lower cost.